The accurate detection of marks or other indicia in documents is important in the presentation of fraud and disreputable handling of such documents. Specifically, with the introduction of high quality colour photocopying, the simple copying of banknotes has presented an immediate need for arrangements to prevent such reproductions. Whilst watermarking and holography have been used in some currencies, with relative success, not all banknotes or other valuable instruments (eg. stock certificates, bonds etc) are similarly protected.
European Patent Publication No. EP 0744 705A2 discloses an image detection system that stores templates of image portions and compares those templates against regions of the image at various rotations.